The world's oceans reached their highest temperatures ever recorded during the weekend, with global ocean temperatures hitting 21.1 degrees Celsius, or 70 degrees Fahrenheit, on Friday and Saturday, according to Samantha Burgess, strategic lead for climate at Copernicus. The heat, driven by a growing natural El Nino and by human-caused climate change, is already stressing life in the water and on land, while the people who depend on the sea are left to absorb the damage.
Who Pays for the Heat
Burgess said the oceans are likely to warm further in the coming months. She called the record "another sign that our climate system is under strain and that the ocean is under immense pressure." That pressure doesn't stay abstract for long. Burgess said warming water becomes more acidic and contains less oxygen, which hurts food industries that depend on the sea. She also said it changes ocean currents and weather patterns, giving storms more power to dump more rain and making storm surges larger.
Jane Lubchenco, an oceanographer and former head of the U.S. National Oceanic and Atmospheric Administration, called the record "very concerning." In an email, she wrote: "A warm ocean destabilizes weather patterns and threatens food security, economic prosperity and marine life. A warmer ocean is not our friend." The language is blunt because the damage is blunt. The ocean doesn't just warm; it rearranges the terms of survival for everyone below the level of decision-makers.
The System Keeps Heating Up
Burgess said the record is especially unusual because, normally, the global sea-surface temperature peaks in March and April, when austral summer ends. This year, the record was set in August. She said the oceans will keep warming until the current El Nino reaches its peak, expected sometime between November and January. El Nino is already the same magnitude as recent events and continues to grow, and Burgess said it is expected to reach unprecedented levels at its peak.
She also said long-term warming from burning coal, oil and gas has raised water temperatures by 0.8 C, or 1.4 F. That's the industrial order speaking in numbers. The fuel economy built by bosses and states doesn't just poison the air; it heats the sea, then acts surprised when the sea stops behaving like a machine built for profit.
Boris Worm, a professor of biology at Dalhousie University in Canada, said: "What breaks my heart is that this starts so early and is so far out of the ordinary that you know when it peaks, it's going to be unprecedented." He added: "It's just that normal doesn't exist anymore." John Bruno, a marine ecologist at the University of North Carolina, said: "It's scary." He said: "We're not even in October. Usually the Caribbean peaks toward the end of September, early October. And I think next year in the Southern Ocean, the Great Barrier Reef... yeah, I'm really worried about what's going to happen in the Southern Hemisphere in February and March."
What Collapses First
Bruno said the amount of heat-sensitive coral still alive today is about one-fifth of 1990s levels, though some coral species, especially the herb-like ones rather than iconic long-lived species such as staghorn coral, are adapting to warmer water and the feared annihilation event has not occurred. Even that small note of adaptation sits inside a larger wreckage. Bruno and Worm warned about fishery collapse and food shortages.
They cited the world's largest fishery, the Peruvian anchoveta fishery, which usually collapses during El Nino and is especially likely to do so in this heat, Worm said. That disrupts the food web because larger fish, marine mammals and seabirds feed on anchovies. Worm said that when water warms, larger creatures can swim to cooler waters, traveling half an ocean, but anchovies can't leave, so they simply don't reproduce or starve. That affects seabirds and even humans who depend on them.
Worm said: "Not everybody is affected equally, obviously, but the whole system collapses." He added: "It's like when you take the stability out of an economy. It's like everything falls apart. Some sectors may do a little better, but overall everybody suffers." The comparison lands because the hierarchy does too. Some can move. Some can adapt. Others are trapped where the heat hits hardest.
Burgess said that as waters warm off Europe, people are seeing more jellyfish, and Bruno said the same may be happening on the U.S. East Coast. Worm said: "Jellyfish are usually opportunistic and like warm waters. So yes, I'd expect them to do a little better." Rick Spinrad, another former NOAA chief, said the ocean is the planet's thermostat, so "while we depend on a healthy ocean for our security, prosperity and well-being, these record sea surface temperatures presage even greater challenges for all of us."
AP said its climate and environmental coverage receives financial support from multiple private foundations and that AP is solely responsible for all content. It also said the story was translated from English by an AP editor with the help of a generative AI tool. The machinery around the story has its own sponsors. The ocean, meanwhile, keeps the receipts.